So you want to make money from an app that you are yet to develop and you do not know how to code. Am I right? Let me answer your multi part question
1. Making money off of Android is not easy. The play store is chocked with half baked apps all clamoring to be on the trending or new list. Any new app that is uploaded to Google Play gets love for a week or so from Google and than starts slipping in rankings if the downloads, reviews, active users, install/uninstall ratios are not good. If you can make your app popular (buying advertisements, reviews or marketing through facebook etc) you can start bringing in some money.
2. For free apps you can earn through banner, interstitial ads, icon ads, push ads. Each of them has their pros and cons but the ECPM is not any where near what you can get from say, Adsense. To make bank you have to have lots of downloads and active users. If you can do that, you will laugh all the way to bank.
3. I do not agree with people who are saying that you can develop apps with phonegap, appcelerator or any other app generators. If you value your sanity and time stay away from them. If you want your app to make people happy, develop it in native code only. Java or C++ is the only way. The performance of a native app is an order of magnitude better than non native apps. Facebook tried creating their flagship app for Android with HTML5 etc and had eggs on their faces.
4. To create an app you will need
a. Knowledge of programming (theory)
b. you must know Java
c. You should have Eclipse and the Android SDK.
Let me tell you, Android development is easy if you know what you are doing but the framework is quirky in it's own way. So to summarise, if you are sure your app will fulfill an unmet or under-met demand , go ahead and create an app but create it in Java (no html, javascript, HTML 5)
